The present invention relates to autonomous vehicles and communication nodes, and more particularly, to methods and systems of operating autonomous vehicles or robots in a transit system containing readable and re-writeable communication nodes.
Autonomous vehicles, i.e., vehicles reacting and responding independently in an environment, are widely pervasive. Conventional autonomous vehicles often contain a complex array of sensors and control systems to navigate and operate in a known or unknown environment. When the conventional autonomous vehicle is introduced into an environment, the conventional autonomous vehicle uses its complex array of sensors to gather information regarding the environment, such as the distance to a wall or the slope of a hill. The conventional autonomous vehicle then uses its control systems to navigate the environment based on the information gathered from its array of sensors.
In order to navigate an environment, conventional autonomous vehicles typically maintain a record of the vehicle""s own position within the environment. Odometer sensors are widely used for this purpose by measuring the motion of the autonomous vehicle""s actuation systems to estimate relative distances traveled from a specific position. However, imperfect mechanical motion over terrain in the environment introduces small errors in the measurements made by the odometer sensors. These small errors continuously compound as the autonomous vehicle moves and thus over time a substantial error occurs. Even with expensive and complex sensor systems, it often becomes difficult for a conventional autonomous vehicle within a moderately complex and irregular environment to determine its position within the environment. One example is described in Garibotto et al. (U.S. Pat. No. 5,911,767) in which Garibotto et al. describes a navigation system for an autonomous mobile robot.
To facilitate and enhance an autonomous vehicle""s ability to navigate an environment, especially a moderately complex and irregular environment, communication nodes such as beacons are generally utilized. Conventionally, beacons are placed in predetermined positions in the environment that are known to the autonomous vehicle. Beacons may be passive or active and often contain unique coded information that enables the autonomous vehicle to distinguish one beacon from another. The unique coded information is associated with a position in the environment that is known by the autonomous vehicle. Hence, when a beacon is detected, the autonomous vehicle uses a lookup table to correspond the coded information with a position in the environment. The detection and analysis of a single or multiple beacons allows the vehicle to determine its own position in a global reference frame or map of the environment.
However, the described beacon based navigation system requires that each autonomous vehicle have access to a pre-established map of the environment with the positions of the beacons recorded in the map. For example, Taivalkoski et al. (U.S. Pat. No. 4,821,192) describes a node map system for a vehicle and Kadonoff et al. (U.S. Pat. No. 4,829,442) describes a beacon navigation system for guiding a vehicle. The pre-established map is either stored in an on-board memory of each vehicle or transmitted to each vehicle from a central system using a wireless communication link. Both of these local and remote storage options, however, add complexity and cost to the autonomous vehicle. For instance, a change in the environment requires a change to the map, usually a manual change, which greatly limits the autonomy and extensibility of the vehicle navigating in a changing environment.
To further facilitate and enhance an autonomous vehicle""s ability to navigate an environment, communication and cooperation between multiple autonomous vehicles is sometimes utilized. The communication and cooperation between multiple autonomous vehicles are commonly achieved using a wireless communication link between each of the vehicles and a central control system. Each vehicle must be capable of generating a communication signal powerful enough to reach a central control system. Thus, each vehicle has an on-board communication system that consumes substantial amounts of power which increases at longer ranges between the vehicles and the central control system. Furthermore, the central control system becomes increasingly complex and costly as the number of vehicles increases.
Thus, both conventional autonomous vehicles and conventional communication nodes used in combination are often complex and expensive in construction and operation. Also, the combination of a conventional autonomous vehicle and communication node are limited in the extensibility of their operation. Accordingly, methods and systems which overcome the obstacles of providing a cost-effective, decentralized and low power communication node and autonomous vehicle combination that include the advantages in extension of capabilities and effectiveness of operation of the combination with no range limitations are desirable.
The present invention provides methods and systems of a transit system containing autonomous vehicles and readable and re-writeable communication nodes that share information with each other. The methods and systems of the transit system provide a cost-effective, de-centralized and low power combination of vehicles and communication nodes which additionally provides extended capabilities and flexibility of operation of the transit system.
A transit system includes a plurality of communication nodes. Each of the plurality of communication nodes includes a node memory able to store information, a node communication device configured to receive information, and a node controller coupled to the node memory and the node communication device. The transit system also preferably includes a plurality of vehicles. Each of the plurality of vehicles includes a vehicle communication device able to transmit information, and a vehicle controller coupled to the vehicle communication device. The vehicle controller is configured to cause the vehicle communication device to transmit information to one of the plurality of communication nodes.
A feature of the present invention is that the node controller of the one of the plurality of communication nodes is configured to update portions of the node memory with information from a first one of the plurality of vehicles. An advantage of this feature is that vehicles are able to share information with each other without being in close proximity of each other. Also, information about the environment, other vehicles, control data, position, or other similar types of information can be distributed throughout the plurality of communication nodes. Therefore, the node memory of each of the communication nodes can be comparatively small to store information about portions of the environment, communication nodes and vehicles, instead of information about the entire environment, communication nodes, and vehicles. Furthermore, the information stored in the node memory can be continually and dynamically updated or refreshed by each passing vehicle operating in the transit system. Therefore, a large high-power transmitter and central control station to update each communication node or manually changing information on each communication node is not needed.
Additionally, in one embodiment, the information includes messages for a second one of the plurality of vehicles from a first one of the plurality of vehicles. An advantage of this feature is that vehicles are able to communicate to with one another without being in close proximity of each other. Likewise, since communication between vehicles is accomplished through the communication nodes, vehicles are able to use low power communication devices with a limited communication range.
In one embodiment, the vehicle controller of each of the plurality of vehicles is also configured to manipulate each of the plurality of vehicles according to the information transmitted. An advantage of this feature is that each vehicle is capable of being provided vehicle control data by a communication node. This allows the vehicle the ability to operate without an on-board computer program or a limited computer program and thereby saving cost and power.
In another embodiment, the vehicle controller of one of the plurality of vehicles is also configured to determine positional information of a first one of the plurality of communication nodes based on the absolute position of the one of the plurality of vehicles. The positional information of the first one of the plurality of communication nodes is transmitted to a second one of the plurality of communication nodes by the vehicle communication device of one of the plurality of vehicles.
A feature of the present invention is that the node controller of the second one of the plurality of communication nodes updates its node memory with the transmitted positional information. An advantage of this feature is that the paths or links logically mapped out by an array of communication nodes is changeable without updating a central map and propagating the central map to all the vehicles. Furthermore, this feature illustrates the advantage that a central map is not needed.
In yet another embodiment, the node memory of one of the plurality of communication nodes stores information that includes environmental data and the node communication device of the one of the plurality of communication nodes transmits the environmental data. This feature of the present invention provides the advantage that information about the environment is capable of being stored and conveyed to one or more vehicles operating in the transit system.
Many of the attendant features of this invention will be more readily appreciated as the same becomes better understood by reference to the following detailed description and considered in connection with the accompanying drawings in which like reference symbols designate like parts throughout.